Excerpts from the Catechism of the Catholic Church

2362 “The acts in marriage by which the intimate and chaste union of the spouses takes place are noble and honorable; the truly human performance of these acts fosters the self-giving they signify and enriches the spouses in joy and gratitude.” Sexuality is a source of joy and pleasure: The Creator himself... established that in the [generative] function, spouses should experience pleasure and enjoyment of the body and spirit. Therefore, the spouses do nothing evil in seeking this pleasure and enjoyment. They accept what the Creator has intended for them. At the same time, spouses should know how to keep themselves within the limits of just moderation.

2363 The spouses’ union achieves the twofold end of marriage: the good of the spouses themselves and the transmission of life. These two values of marriage cannot be separated without altering the couple’s spiritual life and compromising the goods of marriage and the future of the family. The conjugal love of man and woman thus stands under the twofold obligation of fidelity and fecundity.

2364 ...Both give themselves definitively and totally to one another...

2366 Fecundity is a gift, an end of marriage, for conjugal love naturally tends to be fruitful. A child does not come from outside as something added on to the mutual love of the spouses, but springs from the very heart of the mutual giving, as its fruit and fulfillment. So the Church, which is “on the side of life,” teaches that “it is necessary that each and every marriage act remain ordered per se to the procreation of human life.” “This particular doctrine, expounded on numerous occasions by the Magisterium, is based on the inseparable connection, established by God, which man on his own initiative may not break, between the unitive significance and the procreative significance which are both inherent to the marriage act.”

2368 A particular aspect of this responsibility concerns the regulation of procreation. For just reasons, spouses may wish to space the births of their children. It is their duty to make certain that their desires is not motivated by selfishness but is in the conformity with the generosity appropriate to responsible parenthood. Moreover, they should conform their behavior to the objective criteria of morality: ...

2370 Period continence, that is, the methods of birth regulation based on self-observation and the use of infertile periods, is in conformity with the objective criteria of morality. These methods respect the bodies of the spouses, encourages tenderness between them, and favor the education of authentic freedom. In contrast, “every action which, whether in anticipation of the conjugal act, or in its accomplishment, or in the development of its natural consequences, proposes, whether as an end or as a means, to render procreation impossible” is intrinsically evil: ...

2399 The regulation of births represents one of the aspects of responsible fatherhood and motherhood. Legitimate intentions on the part of the spouses do not justify recourse to morally unacceptable means (for example, direct sterilization or contraception).

372 By transmitting human life to their descendants, man and woman as spouses and parents cooperate in a unique way in the Creator’s work.

1643 “Conjugal love involves a totality, in which all the elements of the person enter - appeal of the body and instinct, power of feeling and affectivity, aspiration of the spirit and of the will. It aims as a deeply personal unity, a unity that, beyond union in one flesh, leads to a forming one heart and soul; it demands indissolubility and fruitfulness in definitive mutual giving; and it is open to fertility.”

1652 “By its very nature the institution of marriage and married love is ordered to the procreation and education of the offspring and it is in them that it finds its crowning glory.”

2378 A child is not something owed to one, but is a gift. ...

1654 Spouses to whom God has not granted children can nevertheless have a conjugal life full of meaning, in both human and Christian terms. Their marriage can radiate a fruitfulness of charity, of hospitality, and of sacrifice.